Unexpected leeway by the judge at Leeds crown court saw an hour's final evidence from a primary schoolteacher added to yesterday's dossier of environmental justifications for the hijack presented to the jury of seven women and five men.

Grainne Gannon, 26, of London, who boarded the train near Drax power station in North Yorkshire dressed as a coalminer's warning canary, reinforced points made yesterday by a filmmaker, a charity worker and a university lecturer who said the 22 defendants acted to prevent "deadly and urgent threat" caused by burning coal at Drax powerstation.

Although Judge Spencer repeated many previous warnings that such wider evidence was inadmissible, he did not stop Gannon from describing at length a book about dinosaurs and climate change, nor her conclusion that "burning coal means carbon pollution which means death."

The judge's patience has been mirrored by politeness from the accused, who are defending themselves, and Gannon was reminded several times by her fellow-protester Robin Gillett, who took her through her evidence, to relate her comments to what happened to the train in June last year.

The court adjourned after the lead spokesman in the defence team Dr Paul Chatterton, a Leeds University geography lecturer who was also on the train, told the judge that they felt enough evidence had been heard. The defence will make final statements later this morning, followed by the prosecution.

Judge Spencer will then sum up, and is certain to repeat to the jury that their task is decided what happened and ignore the motives. The action delayed the arrival of 42,000 tonnes of coal at Drax for 16 hours, disrupted passenger and freight services for two days and cost £30,000 to clear up coal shovelled onto the tracks by the protesters.

The defendants have pleaded not guilty to obstructing a railway engine contrary to the Malicious Damage Act of 1861.